Intraoperative mapping of sacral nervous system (S2-4)

Area of Science:

• Neurosurgery
• Neurophysiology
• Spinal Cord Medicine

Background:

• Conus medullaris and cauda equina lesions present complex surgical challenges.
• Accurate identification of sacral neural elements is crucial for preserving function.

Purpose of the Study:

• To evaluate the feasibility and utility of intraoperative electrophysiological mapping of sacral nerve roots (S2-4).
• To assess the effectiveness of this technique in patients undergoing surgery for conus and cauda equina lesions.

Main Methods:

• Intraoperative direct monopolar stimulation of sacral neural elements (S2-4) in 80 patients.
• Recording of compound muscle action potentials (CMAPs) from the external anal sphincter (EAS) under controlled muscle relaxation.
• Mapping was performed during procedures like lipomyelomeningocele dissection, tumor excision, and filum terminale untethering.

Main Results:

• Successful electrophysiological mapping was achieved in 86.25% (69/80) of patients.
• CMAPs were elicited in 82.5% (33/40) of patients with preoperative S2-4 deficits.
• Nerve root identification aided surgical dissection and prevented sectioning of functional filum terminale in three cases.

Conclusions:

• Intraoperative mapping of S2-4 nerve roots is feasible in most patients, including those with neurological deficits.
• This technique is valuable for sparing viable nerve roots and identifying functional neural structures during conus and cauda equina surgery.